Telephone system



July 14, 1931.

J, w. GOQDERHAM TLPHONE SYSTEM Fil'edAug.A 20. 1930 2 sheets-Sheet 1 ATTORNEY July 14,1931.;l w.- GODERHAM TELEPHONE SYSTEM Filled Aug. 20, 1930 -IIHI' IIk-lll NVE/vrai? y JW Gooo'ERHAM A770@ if Nd, Tw @wm www Sw Patented July 14, 1931 UNITED ySTATES Appleman feed August 20, lese. seriales. 42ans.

lThis invention'relates to. telephone systems and particularly to systems involving both automatic switches and operators. circuits for establishing connections, and in which l the service charges are assessed by registers associated with the subscribers lines.

The objects of the invention. are to safeguard the` subscribers against false operation oftheirregisters when certain kinds( of calls are made, to enable the substitutionl Vof a Speeel resister @Pere-eins battery fer the regular battery without interfering with the usual operation of the system, and to otherwise improve. systems of this character. Y

It has been proposed heretoiorey to charge the subscriber'for Vthe service hercceives by means of a register located at the substation and arranged to be operated periodically during theconversation by reversals of current supplied to the subscribers line Afrom the talking battery. When the subscriberls line is extended overaselector switch to a trunk leading to an operators position, the operator responds by inserting the plug of one of her circuits in the jack'in which the trunk terminates. This causes a ilow of current to the trunk in such a direction as to operate a polarized relay to cause the subscribers linel to beextended .directly through the selector'switch to the source of currentin the o .erators cord circuit. In order that the connection may be held under the control of the subscriber after the operator 'has disconnected, it is necessary to associate a source of current with the vtrunk circuit.v This source, which is normally connected'to the trunk in such a directien'as not. to affect the polarized relay when the connection is eX- tended thereto, is disconnected when the operator answers the call and is again reconnected to the trunk when the operator disconnects. H, therefore, the source is reconnected to the trunk in such a manner as to cause current to flow in its normal direction, this will effectively result in a reversal of current in the subscribers line causing his vregister to operate falsely.

"Accor-ding` to the present invention, the objections above mentioned are overcome by `means of a system in which the current Seuree associated WithAv the epereters trunk is reconnected to the trunk reversed direction if the operator disconnects before the subscriber' replaces his receiver. vThis prevente reversal el eurrent in the subeeribere line and the consequent falseioperation of his register. i i Y e feature 'of the inventen is e System in which the Operate? may elect to charge the Subleerber fer the Conversation by throwing a charge key which disables the regular source of talking `current and substitutes therefor a special source of current which is subieet te Periede reversals Sieee there iS a substantial difference inthe potentials of the regular .Seuree and the chers-ins Seuree of current, the circuits are so arranged that the @referti-0H ef the, epereters key else bringe' about the substitution 0f e Special euiee'ryeery relay lier the regular supervisory relay.

In the dlewllg, Fig l dSelOSeS elf-Subscribers line terminating in an automatic oiiice and also a line finder and iirst selector switch, a portion only oi thecircuits fer these Switeh'ee `bein illustrated. 'This isere else illustrates, iesrammatieally e -central olice controlling sender. Fig. 2A illustrates 1n diagrammatic manner other selector switches to which the selector of Fig. 1 has access for the extension of a connec- -tion automatically. Fig. 2 also shows a trunk` extending to an operatos position together with an operators cord circuit by 'means of which connectionsmay be extended over trunks to manual positions or lines,

or over other trunks through automatic switches to subscribersl lines.

AThe finder and selector switches shown in this disclosure may be of the type usually known as panel switches, the detailed conlocated at the substations which respond to periodic reversals of current in the lineduring intervals of conversation to operate a registering train. The substation register is so designed that it remains in either ofv its Yextreme positions until current is again reversed in the subscribers line. One of these registers is illustrated in connection With the subscribers line 100, Fig. 1, and it Will be understood, of course, that other sub- ;scribers lines in the system may be similarly equipped. levices of this character are illustrated in the patents -to Thomson No. 1,121,953, granted December 22, 1914; Bab- .cockNo 1,594,587, vranted'August 8, 1926; 'and Babcock No.

l?? 7 ,210, granted February 18, 1930. y

'itfthe central ofiice, the selector sWitchS is Aequipped with a reversing circuit RV,

which is rendered effective in case thecall V1s tovbe charged and periodically reverses the direction of talking current over ythe tip and Vring conductors of the subscribers line to actuate the substation register 102 once for eachreversal. In case the call is a free one, the reversing mechanism RV remains inert, and talking current is supplied to the calling line continuously in 4a given direction sothat the substation register 102 does not actuate during the conversation. ,The subscriber` may chose to call an operator, either to obtain va connection to which he is Ventitled Without charge, or to ask her assistance in obtaining a connection for rwhich a charge should be made. ln such a case, she dials a designation which causes the selector sivitch S to seize the operators trunk 202-terminating in the jack 203 at the operators position. On such a call to the operator, itis desirable to supply talking current to the calling line from the operators cord circuit C, in which case it is necessary to exclude therepeating `coil and current source at the selector. S and to extend the tip .and ring conductors directly through to the trunk circuit 202 and cord C. It is also desirable that the calling subscriber should have control of the release of the connectionA as Well as the operator.V For this purpose itis necessary to` supply current to the tip andjring conductorsof the subscriberis line through relays associated With the trunk Y202. lVhen, therefore, the switch S seizes the trunk '202, current is supplied tothe tip and. ring conductors 'extending back-to 4the polarized control relay 126 associated With the said switch. The relay 126 should not be operated at this time but should only operate when the operator responds. Accordingly, the direction of current iiow supplied over the trunk 202 is such as not to operate the'relay, 126. When the operator responds byv inserting the plug 214 in the pack 203, relay 126 is caused to operate to advance the sequence switch130 associated With the selector S to exclude the repeating coil 117 and extend the subscribers line directly through to the cord circuit. To accomplish this, it is necessary first to remove the source of current from the trunk 202 and then to substitute therefor a source of current-in the operators 'cord circuit connected in the opposite direction. Since thesubscribers line isnoW connected directly through to the source of current in the operators trunk, the register -102'will assume a position, or Will maintain it if already in that position, determined by the direction ofcurrent flow from the source in the operators cord circuit. l VIf the call is a free one, the register does not. change its position throughout the duration of the conversation, and, When the 'call has been completed, the operator may `Withdraw the `cord before the calling subscriber replaces his receiver to open Lthe line loop. in this event, the current source Vmust be reconnected to the'trunk 202 in order that the connection will not be released until the subscriber replaces his receiver, thereby permitting dhim to recall the operator if heso desires. Since the register 102 is now in the position corresponding to the direction of vcurrent flow from the cord circuit, and

since the source -at the trunk 202 1s normalf ly connected in the opposite direction, the reconnection'ofthis source in its normal direction Would cause the register 102 to make an operation, thus falsely charging the'subscriber. This is` avoideolxbyvso arrangingfin Which the cord circuit source is connected. Accordingly, the subscribers meter is not voperated falsely. ShouldV the call be `one for lWhich the calling subscriber is to be charged, the calling subscriber-s register might also be left, following the last charging operation, in such a position that the reconnection of the source to the trunk 202 in its normal direction Would cause a false operation'of the said register.l

A detailed description will noWbe given of the-operation of the system.- ItWill first be assumed for this purpose that the subscriber of line 100 Wishes to converse With the subscriber of line 201.A In responseto the initiation of the jcall, the allotted line ffizo .finder F responds and operates .toplac'e yits brushes 103, A104 and 105 on the `terminals K`ofthe calling line 100. f l`ollowing this, the

subscribcrs lineis extended overthesprings 1.15 and 116 of sequence switch 130, which has been driven to some position between positions 3 and 11, to the register sender 131. The subscriber thereupon proceeds to manipulate his impulse 1 transmitter 101 -to send the-necessaryimpulses tothe sender 131 .representing the wanted designation. 'lhere- `after brush and group selection at the switch S take place under controlof the sender V131,and the switch S automatically .trunk hunts to seize with its brushes 120,

121 and 122 the terminals of a trunk 200er:- tending to an idle incoming selector switch S-1. The sender next proceeds to selectivelycontrol .the operation-of the incoming` switch S 1 and the final selector switch S-.2 to seize thec-alled subscribers Aline 201. During this time, the sequence switch-130 `moves through successive positions and into some position suchas position 12. In .this (position, the relay 128 is operated in a cir- .cuit'from battery `through its lower winding, upper leftcontact ot' spring 133, contact of spring 132, vconductor 141 to ground in the sender 131. Relayy 128 closes a circuit from battery through the winding of sequence switch magnet 130, contact of se- 1quence switch spring 142, uppercontact o1 relay 128, conductor 143,-upper lett contact of spring 127, lower left Contact. of spring `125 to ground. The sequence switch 130 moves out of position 12 and, according to the natureo'the call, will stop either ,in position y12, 13,14 or :15. l,In the present case it will 'be .assumed that the sequence switch stops in position 14. As :the sequence switch moves .into position 12% a circuit is closed from 4ground,,through the lowercon- 'tacts `of spring i125, conductor 144, through ,the lower contact of relay 123and thence is parallel through the lower winding of said relayto battery and through vsprings 133I and132 and conductor 141 to `the-sender. Examining spring 1215, it will be noted that a similar circuit is `closed in positions 13% and 145/8. These `impulses hold therelay .128 energized and also affect the sender. Vhen the proper number of these impulses have been sent to satisfy the sender, .the

`circuit over conductor 141 is opened `and -relay 128 is .permittedto release, stopping the sequence switch 130. As assumed, the sequence switch 130 in this-case stops in position 14.

As the sequence switch 130 moves yout of position 111/4E and into position 14, the sender 131 is disconnected from the tip and ring conductors 145 and 148 andthese conductors .are extended to the left windings ,of repeating coil 117. The circuit over conductor 145 r may be ltraced through' the lower left .and

upper right contacts of spring `115, .upper left winding of repeating coil 117 to-ground through the upper contactsot relay 112. A

circuit over conductor 146 may be 'traced through the upper left and lower right .con-

tacts of spring` `116, lower left winding lof coil 117, through the lower contacts oit-relay 112 to battery. The right windings of the repeating coil 117 are connected respectively to the tip and ring conductors 25.8 and'259 ot the trunk 200. The circuitover conductor 258 may be traced through the brush r120, upper `contacts of spring 118, upper right winding of coil 117, winding of itlie polarized supervisory relay 126, contacts of` Yspring 124, lower right winding oi the coil Y 117, lowercontacts of spring 119, brush 121 to the. conductor v259. r1`his circuit extends to a source of current inthe incoining'lsesuch that relay 123 does not operate. i

XVhen the called 'subscriber answers, `:the

direction of current in the trunk 200 'is reversed at the selector switch S-l causing .the operation of the polarized relay :126.

As soon after relay 126has operated as `the interruptor 140 closes its right contacts, `a

circuit is completed from battery, through `conductor 148 as above traced. :Relay 129 operates and locks inv a circuit trom its winding and upper contact lthence over conductor 143 toground at sequence switch spring 125. The foregoing operations, including the operation of the linetinder F, the sender v131, and the switches S-l and S2 may all take place in the manner described in detail` in .the above-mentioned patents -to V'Kopp'and Stearn et al., and particularly in the patent to Kopp. Y

The called subscriber having answered, the .connection is now ready for conversation, and .preparation should be made to cause the periodic opera-tion of the calling subscribers register 102. This is accomvplished by substituting the reversing mechanism RV for the direct source .of .talking current at the back contacts of relay 112. With the .relays 12.9 land 139 actuated, afcircuit is closed from battery, through the 'lower winding of relay 112, contacts of spring 123;, conductor 149, lower contacts of relays lector' S-l lie direction, however, being'ls?? 'Y 129 and 139, springs 138 and 137 and thence to ground over conductor 148 as above traced. The relay 112 energizes and connects the tip and ringv conductors 145 and 146 through the impedance coils 108 and 109 and contacts of the reversing relay 107 to battery. This circuit may be traced from conductor 145, through contacts of spring 115, upper left winding of repeating coil 117 upper' front contact of relay 112 to the impedance coil 108. The circuit over conductor 146 may be similarly traced through the contacts of spring 116, lower left winding of coil 117 lowermost front contact of relay 112 to the impedance coil 109. The

' armatures of'relay 112 are so adjusted that ground and battery are connected to the calling subscribers line through resistances 113 and 114 respectively during the brief interval that the uppermost and lowermost armatures of the relay are shifting from their back to their front contacts. rllhis prevents a sudden change of current in the subscribers line; consequently disagreeable sounds in his telephone receiver are avoided. Relay 107 is periodically operated and released by the constantly-driven interrupter 110 to Yreverse the direction of current-over the line at regular intervals.

When conversation is over, the subscribers replace their receivers on the switchhooks, and the finder switch F and selector switches S, S-l and S--2 will restore to their normal positions in the manner described in the above mentioned patents to Kopp and Stearn et al. Should the called party hang up his receiver irst and while relay 107 is operated, relay 112 'is held operated although its operating circuit is opened by relay 126. The holding circuit may be traced from battery, upper front contact of relay 107, upper contacts and upper winding of relay 112, spring 125 to ground. This preventsl false operation of meter 102 should relay 126 be repeatedly operated by the called subscribers switchhook or for any other reason.

It will next be assumed that the subscriber of line 100 calls the operator to assist him in establishing a connection with a subscriber whose line must be reached over automatic switches. It will also be assumed that the call is one to which the subscriber is entitled free of charge. The initiation of the call on the line 100 results in the operation of the line finder F and the association of the sender 131 as hereinbefore explained. The subscriber sets up the record of the wanted designation on the sender, and the selector switch S hunts and seizes an idle trunk 202 extending to the operators position. During the foregoing operations, the sequence switch 130 moves into position 12, and, due to the nature of the designation recorded in the sender, the sequence switch 130 is now driven through positions 13 and 14 and into position 15, which is the position relating to an operators call. With the sequence switch 130 in position 15, a circuit may be traced from battery, through the winding ot relay 206, middle left contacts of relays 205 and 204, brush 120, contacts of spring 118, upper right winding of repeating coil 117, winding of relay 126, contacts of spring 124, lower right winding of coil 117, contacts of spring 119, brush 121, outer left contacts of relays 204 and 205 to ground. The direction of current flow in this circuit is such that the polarized relay 126 does not operate. Relay 206, however, operates and closesa circuit from battery, through its outer contact and the signal lamp 21.1to ground. The lamp 211 illuminates to advise the operator that'a call is waiting on the trunk 202. Relay 206 also completes a circuit from battery, through its inner Contact, winding of slowrelease relay 207 to ground. Relay 207 applies ground potential through resistance 212 to the sleeve conductor 260 to maintain the selector switch Sv busy.v vRelay 207 also closes a circuitfrom the tone source 210,

interrupter 209, lamp 208, condenser 213,

lett' contact of relay 207, right contact of relay 205 and thence to the tip conductor of the trunk 202. Current flowing over the line from this circuit produces a tone at the subscribers station to advise yhim that the operator is being signalled.

. The operator responds to the signal by inserting the plug 214 of the cord circuit C in the jack 203. The insertion of the plug closes a circuitfrom battery through the winding of relay 216, sleeve of the plug and jack, cut-off relay 205 to ground. Relay 205 operates and opens the battery and ground connections to the trunk 202, per- Vmitting the relay 206 to release. Relay 206 eXtinguishes the lampV 211 and opens the circuit of slow-releasing relay 207. Relay 207, however, does not retract lits armatures since a substitute holding circuit is provided as will be presently described. Relay 205 operates the relay 204 in a circuit from battery, through the inner left contact of relay 205, winding of relay 204 to ground. Relay 204 operates and locks in a circuit from battery, through its inner left contact and lett-hand winding to the grounded conductor 260. Relay 204 closes a holding circuit for relay 207 traceable from battery, through the inner left contact of relay 205, right contact of relay 204, to ground through the winding of relay 207. Relay 205 in operating disconnects the tone source 210 from the trunk 202 notifying the calling subscriber that the operator has answered. The

purpose of the relay 204 is to maintain the to; l`the-trunk and V thus avoid Vfalse operation of I'the register -102as hereinafter explained.

jl'Relay `216 also operates in series .with the cut-oil relay l205 and `in so* doiu'ig'com-V plete'sthe tipconduetor lthrough tolthe repeating coil 217 to include a source 'of eur-y rentinthefcord circuit in the loop extendingto the selector switch S. this :purpose `may be tracedy from battery,

Vthrough the resistance 261, supervisory relay outer right-back contact of relayV 235, lovverrll'eft .winding of repeating colll 217 contacts ot-ley 215, ring-of Lthe plug 214 and jack-208, theneeoverthe brush 121 and `las previously traced through the Winding-Aot-the polarized relay y126 Yand returningover brush 4120, throughthe Vtip conA in thisfcircuit? and completes a circuit from battery,:through-theupper winding of relay 128, right contacts of sequenceswitch spring 13.7, .closed in .position 15, conductor 148,V

contact `of relay 126, through the `contacts ofsprings 127 and `125 -to-ground. lRelay.

128 operatesand drives the-sequence switch 118 outof position 15 andintoposition 16 byfmeausot' the circuit traceablel from ybattery,- :through .the Winding of sequence switch-.magnet 130, spring 142, upper cone tactot' relay 128.1to Vthe Agrounded conductor 143. Relay 128 vlocks in a circuitfrom battery, :through .its lower .Winding and loiver. contact, conductor 144, right contaets offsequencefsW-itch spring -125, 'test brush-` 122 to the grounded sleeve conductor 26,0. In position 16, thepolarized rel-ay 126 :and the .repeating coil 117 are excluded from thev circuit, andthe tip and ring conduetors of .thesubSCribers vline .160 are lextended through -thelet't contacts 4of springs 115and 1:16 respectively, directly through tothe tip and `ring conductors `oiijthe trunk 202. The circuit previously .traeed'forfthe supervisoryk relay 242'- is l.thus modiiiedto include the subsoribes loop,fand relay 242 remainsenergized.

lVhen relay 216 operatesas above dei scribed, it closes aY circuit vfrom battery,

through the supervisory lainp227, 'resiste ance228 to ground at the-lower contact of said ,relayl .The lamp 227, .however, is

vprevented from illuminating by meansof a shunt circult traceable from groundyat the' lower Contact of relay 216, through theresistances 228,;and 229, right '.contactof'supervisory relay 242, right bacl; Contact of slow-release relay 241,' left normal contact of relay 246 `to battery through -the right Winding ofrelay 248. .The purpose of relaysf241, 246 and 248 Will be describedmore in detail hereinafter.

The circuit-for:

ductors of the "cord C. .The .actuation of key A222 "also completes, a "circuitl "from f batteryfthroughitheleft Winding of rel'ay 2:41 to groundat .the'ycontacts of key 222. ,"Relay-'241 operates" and locks kin 'a' ci'rcuit":trom

ground, through 'its right Winding `and^75" right iront contaet,"'right Contact of Vrelayj 242 to bjatterythrough theileft contact of relay. 241. 'lhe operator challenges the calling subscriber andV `.obtains 'from him the number of A'the Wanted .line 257, which, "80

it has been assumed, V'is to be reached over the `trunk 256 and succeedingV automatic" switches '(notillustrated ingthis drawing). She thereupon inserts `the lcalling plug 226 of; her cord -circuit in the jack 255`of an idle "85v trunk-256 leading to automatic switches Whichhave access to the called:subscribers linef257. The insertion-ofthe .plug in 'the jack- 255 closes, la circuit -from battery,

through the Winding of relay 219, Winding '90 of relay 218,fsleeve of the plug226and jack to ground. It 'Will be. assumed th'lat'rthe sleeve circuit of theftrunk 256 has a high resistance. f'lherefore, .the marginalrgela'y. 219 does Y not operate. "Relay 218, however, l 95 operates in this circuit andy causes the operation -o relay225 in an "obvious circuit. Relay-225 closesa break point'in `the tip conductor. R'elayf225 `also closes a circuit for the lamp 254-traceable fromfbatter 100 through said lamp., resistance 252 toA at fthe lower contact of said relay.

.ground ,Noxa -the operator `actuates A"the dialfkey 224 toconnect :thel-imp'ulse "contacts of the dial 250 to the '.tipand ring conductorsfof "105 the trunk256`. She thereupon manipulates the dialg2'50 'to sendwimpulses'in the Wellknown` manner toy set the succeeding switches to seize the called subscri'bers"line 257.

The dial and''talkingkeyshavingl beenfre- '.110`r leased, Ithe Voperator signals lthe calledh vsubl scriberibygmeans of her ringing Vkey 223.

Duringthe vestablishment of fthe lconnection, afloop circuiti` is completed extending" rover' the -ti'pv conductor of jthe trunk 256,115 Y through the jacl f`2`55 land .'plugf226, 'through the innerfront-contact of.relay"225 con tactsofleys 224 and 223, upper 'right'vvindling ot'iepeatin coilV 217, u'pperbaclz contact of relay219,*W1nd1ngofthe'polarized supfeiv- 120 visory relay V221, loiver back 'Contact of relay v219, lower rightjwin'ding off repeating -cfoil 217 thence over ythfegring sideofjthegloop.

The Lresponsefof Ithe called subscriber causes a reversal of current `in this `=loopWhich oper:l 125 atesV the relayf221'. iThe relay 221' closes a 'circuit fromV battery, jthrou'gh' ,its contact, ,throughV resistances 25?andf 252 ,to ground. at the Contact orelay 225. This circuitfs'hunts p the lamp 254, which eXtinguishes to 'advise 130 A 5A hook, but it will be' assumed that the calling subscriber delays the replacement of his receiver for an interval. The replacement of the called subscribers receiver results in the release of supervisory relay 221. Relay 221 removes the shunt from lamp 254, and this lamp lights to notify the operator that the called subscriber has replaced his receiver. The operator disconnects by removing the plugs of the cord C from the respective jacks. The removal of the plug 226 opens the circuit of relay 218, and this relay in turn releases the relay 225. Theremoval of plug 214 from the jack 203 opens the circuit of relays 216 and 205, and these relays release. Relay 205 reconnects the relay 206 to the trunk 202, but in this case the circuit extends from battery, through the winding of relay 206, middle left contact of relay 205, middle left front contact of relay 204, over the ring conductor of the trunk 202, and thence over the calling subscribers loop 100 and returning over the tip conductor, through the outer left front contact of relay 204 to ground at the outer left back contact of relay 205. The direction of flow of current in this circuit s the same as prevailed during the time the calling subscribers line was connected to battery through the winding of the relay 242. Accordingly the sub- .scribers register 102 is not falsely operated. Relays 204 and 207 are now held by the relay 206 in a circuit traceable from battery, through the inner contact of relay 206 and thence in parallel through the winding of Vrelay 207 and through the right contact and right-hand winding of relay 204 to ground. The removal ofthe plug 214 also results in the release of relays 242 and 241. When the calling subscriber finally replaces his receiver on the switchhook, the relay 206 releases, and after an interval relay 207 retracts its armatures to remove ground potential from the sleeve conductor 260 and to permit the release of relay 204. The removal of ground potential kfrom the conductor 260 results in the release 0f the selector switch S and the finder switch F.

Assume next that theV called line 257 is one Vthat is reached over a trunk extending to a succeeding manual operators position. Assume also that the sleeve circuit of the trunk extending to the succeeding operators position, such as the trunk 256has a relatively low resistance. When, therefore, the operator inserts thefplugl 226 ofthe cord C in the jack 255, a circuit is completed over the sleeve contacts for the relays 218 and 219 as -hereinbefore described. In this case, Y however, the resistance of the sleeve circuit a being low, the marginal relay 219 operates with the relay 218. Relay 219 extends the tip and ring conductors of the cord circuit through the windings of relay 220 to battery and ground. Relay 220 operates and shunts the supervisory lamp 254 to extinguish it. v

It will be assumed next that the call completed through the operators cord C is one for which the calling subscriber should be charged. To effect this, the operator throws the charge key 244 aftershe has determined the nature of the call. obvious circuit for relay 243. Relay 243 operates and locks through its Winding and leftcontact to ground at the lower contact of relay 216. lThen-the called subscriber answers, either the relay 221 or the relay 220 operates as above explained, and a cir` cuit is completed from battery, through the Contact of the particular one of these relays which is operated, conductor 264, inner right f through its left-hand armature and makesl contact. When the interrupter 232 subsequently closes its contact, a circuit is completed from battery, through said interrupter, lamp 267, outer right contact of relay 266, left winding of relay 235, outer contact f of relay 245 to ground. Relay 235 operates and locks through its'left contact and left winding to ground at the contact of relay 245.l The purpose of relay 235 is to disconv nect the normal source of talking current Y and the supervisory relay 242 from the call- `ing subscrlbers circuit and to substitute therefor the reversing circuit RV-l and the auxiliary supervisory relay 236. vThe substitute circuit for supplying talking cur-l rent may beftraced from the free pole of battery, through the outer left back contact of relay 239, choke vcoil 237, winding of Key 244 closes an supervisory relay 236, outer right front con-V tact of relay 235, thence through the lower left winding of the repeating Vcoil 217, over I the subscribers line and returning through the upper left winding of said repeating coil,

inner right front `contact of relay 235', chokeV coil 238, right-hand armature and back contactof' relay 239 to ground. The relay 239 l is repeatedly operated and released at delinite periodsV by the interrupter 240 to reverse the direction of current How over the 10.' supervisory relay for each source in ordei calling Vsubscribers line to repeatedly ,oper-V f with the reversing circuit vthan the source normally-supplying current from the operatorsco'rd circuit. In view of this difference ofpotential in the two sources of talking current, its is necessary to employ avseparate to .secure a reliable performance for the supervisory relayl underall conditions. This is accomplished byproviding the relay 242 for use in series with the normal source of tal-king current ,and the auxiliary relay 236 for use in series with the source in the reversing circuit RV--L The vrelay 235 in operatingyas explained, removes the-relay 242 and includes the relay 236 when the reversing battery is connected in circuit.

4Should the calling subscriber wish to recall'fthe operator, he may do so by momenf tarilyxdepressing his -switchhook and again releasing it. The depression of the switchhook Vat the calling station opens the line and-releasesthe answering supervisory relay suchfas thevrelay 242. `Relay 242 in turn releases the relay i, 241. When the sivitchhook is again released to close the line loop,

the supervisory relay; 242 reoperates and a circuit is closed from battery, through the right Ywinding of relay 248, left normal contacts Vof relay 246, :right back contact of relay 241, Contact of relay 242, resistances 229;.and 228 to groundV at the contact olf relay 216. This circuit shunts the lamp 227 and causes the relay 248: to operate. YOn the next` closure of the interrupter 249, a circuitiscompleted `to ground through said interrupter, contact lof relay 248, winding ,of relayv246 tobattery. Relay 246 operates and closesa holding circuit for the relay 248 traceabley 'romubatteryu through the right winding of relay 248, leitcontacts of relay "246,-.le:t`twinding of relay 248 to ground.

Relay 246 at its left contacts opensithe previouslyv traced circuit through the right Winding of relay 248 in shunt of the lamp 227, allowing the lamp to illuminate. Relay v246 `at Yitsright contact closes a circuit for thebuzzer 247. Vhen the interrupter 249 opens itscontacts, relays 246 and 248 release, and the shunt is again closed around the lampv227 causing it to extinguish. This flashing ofthe lamp 227 ywill continue until the opeiator `manipulates the talking `key 222 tooperate the relay24l as hereinbefore explained.

-Vhat is claimed is:

'1. Inl a telephone system, a subscribers line, a message register at the substation responsive to the flow of current in said line, an operators position, a trunk leading to said position,` means for 1 extending Vthe sub-"f ljscribers line to-said trunk, asource normal-,.

ly connected-to said trunkto cause theaflow of current in a given direction therein, a cord circuit at Vthe operators position for making connection to said trunk, a source of current in said cord circuit, means responsive tothe connection of said cord to the trunkfor disconnecting said rst source from the trunk and responsive to the discon nection of said cord Vtor reconnecting said lirst -source to said trunk, means responsive tothe connection of said cord to said trunk for extending the ytalking conductors .ot said linethrough tothe source of current in said cord, andineans fer reversingthe connection oi said tirst source to cause current toflow" in the opposite direction in said-.trunk when said -tirst source is reconnected thereto.

l 2. In a telephone system, ,subscribers line,.a message `register at the substation re'- sponsive to the-'flow of current in said line,1

an operators position, a trunk circuit terminating in a jack at said position,- a switch forl extending the subscribers lineto said trunk, afsoui'ce normally connected t0 saidtrunk to causethe fiowof current in a given direction therein, a cord circuitfor `making connection with said trunk, asourceoi-.current in said coid circuit, Vmeans responsive to the-insertion of the plug of :saidcord in said jack for disconnecting said iirst source fromthe trunk and responsive tofthe removal of said plug for reconnectingsaid first sourceA to said trunk, means infsaid switch responsive to Athe insertion of said plug inthe jack for extending thetalking conductors of said linethrou-ghssaid switch to the source of current in said cord circuit,y

and means V:for reversing thefconnections of said first source to cause current to-kiiowin theropposi-te ydirection in said ,trunk circuit' when said first source is reconnected-thereto. 3. Tn a telephone system, a subscriberzs line, a serviceregister responsivetotheflow ofcurrent in said line, an operatorsposition, a trunk circuit leading tosaidposition, means for extending the subscribers line to said trunk, a source normally connectedto saiditrunk to. causethelow of currentV inea given direction itherein,-a cord circuit for making connection-with said tru-nk, a source f in saidcord circuit for causing the i'low of connecting said irstvsource from the trunk and responsive to the vdisconnection ,osaid cord for: reconnecting saidv first source. to said trunk, means responsive tothe connection of said cord to said trunk `tor extending the `talk-ing conductors of saidline through to the source ot cu "rent, in said cord, and .means for .reversing Ythe, connections ofsaid iirst source to .cause f current toA .ilowA in; said tru-nk i.

in the same direction as that caused by the source in said cord circuit;

4. In a telephone system, a telephone line, a service register responsive to the How oi':l talking current in said line, a trunk circuit, an automatic switch for extending said line to said trunk circuit, a source normally connected to said trunk to cause the liow of cur- A rent in a given. direction therein, switching means for making connection to said trunk, a source of current in said switching means, means responsive to the connection of said switching means to the trunk for disconnecting said irst source from the trunk and responsive to the disconnection of said switching means for reconnecting said first source to said trunk, means eliective in response to the connection of said switching means to said trunk for extending the conductors of said telephone line through said automatic switch to the source of current in said switching means, and means for reversing the connection to said first source to said trunk to cause current to flow in` the opposite direction in said trunk, when said rst source is reconnected thereto.

5. In a telephone system, a telephone line, a message register at the subst-ation responsive to the liow of talking current in said line, an opeiators position, a trunk leading to said position, means for extending the telephone line to said trunk, a source normally connected to said trunk to cause the flow of current in a given direction therein, a-cord for making connection to said trunk, a source of current in said cord, a circuit established by the extension of said connection to the trunk for the iow of current from said lirst source, said circuit including said trunk and excluding said telephone line, means responsive to the flow of current in said circuit for signaling the operator, means responsive to the connection of said cord to the trunk for disconnecting said irst source from the trunk and responsive to the disconnection of said cord iior reconnecting said lirst source to said trunk, means re- .sponsive to the connection oi' said cord to said trunk for extending the talking conductors of said line through to the source of current in said cord, and means for reversing the connections of said first source to cause current toow in said line in the same direction as that caused by the source in said cord when said first source is reconnected to the trunk.

6. In a telephone system, a subscribers line, a message register at the substation responsive to the flow of talking current in said line, an operators position, a trunk leading to said position, an automatic switch for extending the subscribers line to said trunk, a source normally connected to said trunk to cause the flow of current in a given direction therein, means responsive to `the normal flow Vof' current in said trunk for holding said automatic switch against release, means responsive to the connection of said cord'to said trunk for' disconnecting.

said Vfirst source from the trunk and'responsive to the disconnection oi the cord forreconnecting said irst source to said trunk, means-responsive to the connection of said cord to said trunk for extending the conductors of said line through said automatic switch to said cord to cause the flow of current from the source in said cord over the conductors of saidline, and means responsive to the connection of said cord to said trunk for reversing the connections of said lirst source to cause current to flow in the opposite direction over said trunk andv line when said lirst 'source is reconnected to the trunk. f

7. Ina telephone system, a subscribers line, a message register responsive to reversals of the flow of talking current in said line, an operators position, a trunk leading to said position, an automatic switch for eX- tending the subscribers line to said trunk, a source of talking current associated with said switch, means for periodically reversing the direction Vof flow of current from said source to operate said message register, a source normally connected to said trunk to cause the flow of current in a given direction therein, a cord circuit for making connection with said trunk, a source of current in said cord circuit, means controlled by said cord circuit for connecting said second source to said trunk and for disconnecting the same from said trunk, means responsive to the connection of said cord to said trunk for extending the conductors of said line through said automatic switch to the source of current in said cord circuit, andmeans for reversing the connections of the source of current associated with said trunk for causing the liow of current in the opposite direction in said trunk when such source isreconnected thereto.

8. In a telephone system, a subscribers' line, a message register associated with said line and responsive to the flow of current therein, an operators position, a trunk leading to said position, a cord circuit at said position for making connection with said trunk, a source in said' cord circuit for supplying talking current to said-line, a supervisory relay incircuit with said source for indicating the condition of the line, a second source associated with said cord for supplying talking current to periodically controlling said second source to cause the operation of said message register, a supervisory relayin circuit with said second source, and means for substituting said second source and the associated supervisory relay forsaid lirst mentioned source and the associated supervisory relay.

said line, means for 9. In a telephone system, a subscribers line, a message register at the substation responsive to reversals of current in said line, an operators position, a trunk leading to said position, a cord circuit at said position for making connection with said trunk, a source associated with said cord for supplying talking currentto said line, a supervisory relay in circuit with said source for indicating the condition of said line, a second source for supplying talking current to said line, means for periodically reversing the direction of current from said second source to cause the repeated operation of said message register, a second supervisory relay in circuit with said second source for indicating the condition of said line, and a key at said position for substituting said second source of current and the associated supervisory relay for said first-mentioned source and associated supervisory relay.

10. In a telephone system, a subscribers line, a message register at the substation responsive to the flow of current in said line, an automatic switch, means for extending the subscribers line to said switch, a source associated with said switch for supplying current to said subscribers line, a register sender for controlling the selective operation of said switch to further extend the connection,

and means controlled by said register sender in accordance with the nature of the connection being extended, for so controlling the How oi' current from said source as to cause the operation of said message register.

ll. In a telephone system, a subscribers line, a register at the substation responsive to reversals of current in said line, an automatic switch, trunks of different classes accessible to said switch, means for extending the subscribers line to said switch, a source of talking current for supplying said line, a register sender for variably controlling the selective operation of said switch to seize trunks of different classes according to the nature of the call, and means controlled by said register sender in accordance with the nature of the call Jfor causing the periodic reversal of said source of current to repeatedly operate said message register.

In witness whereof, I hereunto subscribe my name this 18th day of August, 1930.

JOHN W. GOODERI'IAM. 

